/Engine/Source/Editor/UnrealEd/Public/UnrealWidget.h
Converts mouse movement on the screen to widget axis movement/rotation.
void ConvertMouseMovementToAxisMovement ( [FSceneView](API\Runtime\Engine\FSceneView) * InView, [FEditorViewportClient](API\Editor\UnrealEd\FEditorViewportClient) * InViewportClient, bool bInUsedDragModifier, FVector & InDiff, FVector & OutDrag, FRotator & OutRotation, FVector & OutScale )